The present invention relates to a scroll type fluid machine usable as compression means in refrigeration cycle of air conditioner, refrigerator or the like, for compressing air or other gas, or an expander which produces power through expanding a compressive gas and, more particularly, to a device for pressing the orbitary scroll member against cooperating scroll member in the scroll type fluid machine.
In, for example, U.S. Pat. No. 3,884,599, an axial sealing means for attaining a seal between opposing axial end surfaces of two scroll members of a scroll type fluid machine is proposed wherein gas derived from the working chamber, having a pressure of the highest level in the closed loop, is applied to the back surface of the orbitary scroll member opposite to the cooperating scroll member. Usually, the discharge port of the scroll type compressor is connected to a load such as a condenser and the pressure of the gas at the discharge port varies with the change in the operating condition, so that the axial pressing force exterted by the gas on the back surface of the orbitary scroll member fluctuates enough to unstabilize the orbiting movement of the orbitary scroll member, resulting in an unsmooth and unreliable compression. It is to be noted also that, if the suction pressure is changed while the pressure at the discharge port is maintained constant, the separating force tending to separate the two scroll members from each other produced by the gas confined between two scroll members varies so as to cause an unbalance between the force tending to separate two scroll members and the force tending to press the orbiting scroll member, also resulting in an inferior compression.
In U.S. patent application Ser. No. 139,548 a scroll type fluid machine arrangement is proposed which utilizes the gas derived from the working chamber during a compression or expansion to act on the back surface of the orbiting scroll member. The pressure in the working chamber, however, varies in accordance with the change in the suction pressure, so that the axial pressing force acting on the orbiting scroll member is changed conveniently in response to the change in the suction pressure. In this case, therefore, it is possible to maintain stable compression in spite of change in the suction pressure. This stable compression, however, can be obtained only within a limited range of the discharge pressure because, in this case, there is no means to relate the discharge pressure to the internal pressure of the working chamber.
In the equipment having a so-called inlet by-pass type capacity control system, the pressure in the working chamber is reduced to a level below that required for pressing the orbiting scroll member against cooperating scroll member, when the capacity control is actually made. In such a case, it is not possible to effect good seal between the opposing axial end surfaces of two scroll members.
Accordingly, it is a primary object of the invention to provide a device for imparting axial pressing force on the orbiting scroll member of a scroll type fluid machine, improved to ensure an efficient seal between the axial end surfaces of the scroll members.
It is another object of the invention to provide a device for imparting axial pressing force on the orbiting scroll member of a scroll type fluid machine, capable of minimizing the loss of power due to friction.
It is still another object of the invention to provide a device for imparting axial pressing force to the orbitary member of a scroll type fluid machine, which can maintain a suitable axial pressing force even when a capacity control is made by allowing the gas in the closed working chamber to flow directly to the low pressure side by-passing the load.
It is a further object of the invention to provide an improved device for imparting axial pressing force to the orbiting scroll member of a scroll type fluid machine to diminish the deformation of the orbiting scroll member.
It is a still further object of the invention to provide a device for imparting axial pressing force to the orbiting scroll member of a scroll type fluid machine, which can suitably be applied to a compressor having a lubricating system.
It is a still further object of the invention to provide a device for imparting axial pressing force to the orbiting scroll member of a scroll type fluid machine, which can suitably be applied to a compressor of the type in which a compression element and an electric motor for driving the compressor are housed by a common closed container.
It is a still further object of the invention to provide a device for imparting axial pressing force to the orbiting scroll member of a scroll type fluid machine which permits an easy formation of a lubricating oil passage through which a lubricating oil is supplied to the sliding surfaces between two scroll members.
It is a still further object of the invention to provide a device for imparting axial pressing force to the orbiting scroll member of a scroll type fluid machine, which can suitably be applied to a compressor capable of operating in two modes, namely, compression modes as in the case of the cooling and heating operations of a heat pump type air conditioner.
It is a still further object of the invention to provide a device for imparting axial pressing force to the orbiting scroll member of a scroll type fluid machine, suitable for use in a scroll type fluid machine in which the suction pressure and discharge pressure are varied over wide ranges.
To these ends, the present invention provides a device for imparting axial pressing force to the orbiting scroll member of a scroll type fluid machine which is of the type having two scroll members each having a spiral wrap and an end plate, the scroll members being coupled with each other such that their wraps mate with each other, one of the scroll members being adapted to make an orbiting movement relatively to the other without rotating around its own axis, to thereby form at least one working chamber of different pressures between two scroll members. At least two pressing force imparting chambers are formed on the side of the orbiting scroll member opposite to the wrap, with the pressing force imparting chambers including a first chamber which is communicated through a communication passage with at least one of the working chambers which are materially isolated from the low-pressure port and isolated from the high pressure port, and a second chamber which is communicated through a high pressure port through a passage, so that different fluid pressures are applied to the first and second pressing force imparting chambers.
These and other objects, features and advantages of the invention will become clear from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.